How to Join Two Pieces of EPDM for Ponds

EPDM pieces can be joined to line an irregularly shaped, large pond.

EPDM, ethylene propylene diene Monomer, is a type of synthetic rubber commonly used as a liner for garden ponds. The rubber sheets contour to any shape pond and leave few folds. While EPDM pond liners are sold in many sizes, as well as in customized sizes and shapes, sometimes it is more practical to join two liners; for example, if you already have the liner but need to customize it to fit an irregular-shaped pond. The ability to adhere two liner edges together can also come in handy when you want to salvage a torn liner.

1

Cut the two pieces to be joined so the edges are perfectly straight and will line up on the tape. Use a razor knife to cut a clean line. Spread the pieces out on a flat work surface or a clean driveway if joining two large pieces.

2

Clean each piece of the EPDM liner with rubbing alcohol to remove all dirt and prepare the surface so the tape will stick. It may take several attempts, using several rags to thoroughly clean the liner, but this is essential for a strong bond. You don't necessarily have to clean the entire piece, but clean a strip at least 12 inches wide on the front and back of each piece where they will connect.

3

Brush EPDM tape primer along the top edge of the first liner piece, using a disposable paintbrush. Apply the primer in a 6-inch wide strip along the entire length of the liner. You might need to wait about 10 minutes for the primer to activate before applying EPDM tape. Read the EPDM tape label carefully to determine if primer is required for your particular brand.

4

Unroll a piece of 6-inch wide, double-sided EPDM liner tape and apply it to the top edge of one liner piece. Peel back just a small flap of the paper backing, line up the tap with the edge of the liner, and press it down securely. Peel off the backing as you unroll the tape, which makes it easier to keep the tape lined up with the edge and prevent wrinkles.

5

Fold the edge of the second liner piece back about 1 foot to reveal the back side of the liner -- the edge that will connect with the other piece of liner. Apply a 6-inch wide strip of EPDM tape primer to the bottom edge and wait about 10 minutes for the primer to activate.

6

Peel the paper backing from the second side of tape; pull it up from the entire length of tape. Avoid touching the tape while you work because this can affect the adhesive ability. The tape primer should be activated by the time you finish this task.

7

Line up the bottom of the second piece of liner over the tape, overlapping the edges by 6 inches. Just as when applying the tape, start at one corner of the second piece, line it up with the tape and slowly work your way to the opposite end.

8

Roll out air bubbles and press the lines tightly against the tape, using a seam roller for pond liners. Roll from the center of the seam toward the edges of each piece so the air bubbles can escape.

9

Check the liner for a tight seal after several minutes. Heat the seam with a hair dryer to soften the adhesive and roll it a second time, if needed.

10

Apply a bead of lap sealant for rubber liners along the edge of each piece of the liner to further waterproof the seam. These come in tubes that you can use in any caulking gun. Apply the sealant to one side and allow a few hours for it to dry before flipping over the liner and applying it to the other side. Allow at least 24 hours for the sealant and tape to cure before using the pond liner. Alternatively, you can cover each seam with a strip of single-sided EPDM tape applied over an application of primer.

Things You Will Need

Measuring tape

Rubbing alcohol

Cleaning rags

EPDM splicing tape

Pond liner seam roller

Tip

Some EPDM pond liners might recommend the use of glue to ensure the tape sticks to the liner. Read the liner and tape labels carefully to see if this is necessary. If glue is needed, use an clean paintbrush to brush an even coat all over the top of the first liner before applying the tape. If adhesive is needed on the second piece of liner, bend the liner back to expose the bottom edge, brush on a coat of adhesive and press the liner onto the tape.

Allow the liners to dry completely between cleaning the liners and applying the tape or they won't seal properly.

About the Author

A former cake decorator and competitive horticulturist, Amelia Allonsy is most at home in the kitchen or with her hands in the dirt. She received her Bachelor's degree from West Virginia University. Her work has been published in the San Francisco Chronicle and on other websites.